Ink pad tensioner for stencil duplicators



Dec. 15, 1959 E. H. DU Bols 2,916,990

INK PAD TENSIONER FOR STENCIL DUPLICATORS Filed Sept. 11, 1957 3Sheets-Sheet 1 Dec- 15. 1959 E. H. DU Bols 2,916,990

INK PAD TENSIONER FOR STENCIL DUPLICATORS Filed Sept( l1, 1957 3Sheets-Sheet 2 'l Il IN VEN TOR.

in m De@ 15, 1959 E. H. DU Bols 2,916,990

INK PAD TENSIONER FOR STENCIL DUPLICATORS Filed Sept. 11. 1957 5Sheets-Sheet 3 United tates iiatent mit ran rizNsioNnR For: sTENCiLnUPLicArons Chicago, Ill., assigner to A. B. ick

Edgar H. Du Bois,

iii., a corporation of Iilinois This invention relates to duplicators orother printing machines and pertains particularly to stencil duplicatorsin which a stencil is wrapped around an ink pad which is held undertension on a printing drum or cylinder.

One object of the present invention is to provide a new and improvedmechanism for holding an ink pad under tension on the printing drum of astencil duplicator.

Another object is to provide a new and improved ink pad tensioningmechanism which is easy to operate so that the operator may readilyremove and replace the ink ad. p A further object is to provide an inkpad tensioning mechanism which is arranged to distribute the tensionevenly on the ink pad along its width.

Another object is to provide a new and improved ink pad tensioningmechanism which is easy to manufacture and low in cost.

Further objects and advantages of the present invention will appear fromthe following description, taken with the accompanying drawings, inwhich:

Fig. 1 is an end view of a printing drum or cylinder for a stencil typeduplicator, equipped with an ink pad tensioning mechanism to bedescribed as an illustrative embodiment of the present invention.

Fig. 2 is a fragmentary elevational view of the tensioning mechanism,taken generally as indicated by a line 2-2 in Fig. l, the mechanismbeing shown in its rest position, occupied when there is no ink pad onthe drum.

Fig. 3 is a view somewhat similar to Fig. 2, but on a larger scale andwith the mechanism in its normal operating position, with an ink padbeing held under tension by the mechanism.

Fig. 4 is a fragmentary enlarged section View taken generally along aline 4 4 in Fig. 3.

Fig. 5 is a View somewhat similar to Fig. 3, but with the mechanism inits ink pad releasing position.

Fig. 6 is a fragmentary end view showing the tensioning mechanism withparts of the cylinder broken away.

Fig. 7 is a fragmentary enlarged sectional view, taken generally along aline 7--7 in Fig. 2.

It will be seen that the drawings illustrate an ink drum or cylinder 10for a stencil type duplicator. It will be recognized that cylinder 10 isof the closed type forming a tank or reservoir adapted to hold a supplyof ink. A large part of the peripheral surface of cylinder 10 is formedby a cylindrieally curved, perforated diaphragm 12. An ink pad 14 may bewrapped around the perfo rated diaphragm 12 and may be tensioned on thecylinder 10 by means to be described in detail shortly. A printingmaster in the form of a stencil (not shown) may be wrapped around thecylinder 10 over the ink pad 14. It will be understood that the inkpasses from the inside of the drum lil through the perforated diaphragm12 and wets the ink pad, so that the ink pad becomes saturated with ink.The ink from the ink pad passes through the openings in the stencil andis transferred to copy sheets which are pressed against the drum 10 inthe course of the printing operation.

Patented Dec. 15, 1959 ice The present invention is concerned with themanner in which the ink pad 14 is held under tension on the printingdrum 10. At its head end, the ink pad 14 is simply anchored by beinghooked over a plurality of studs, or hooks 16, which are securelymounted on the drum 10. Thus, the studs 16 are immovable with respect todrum 10. An apertured bar 18 is secured to the head end of the ink pad14- and is adapted to be hooked over the studs 16. The studs are mountedon a wall 20 which is receded in position with respect to the extendedcircle of the diaphra-gm 12 so that the studs will not come into contactwith the copy sheets or other parts of the duplieating machine.

The tail end of the stencil 14 is also tted with a reinforcing bar 22,made of sheet metal or other suitable material. A plurality of apertures24 are formed in the bar 22 and are distributed along the width of theink pad 14. The tail end of the ink pad 14 is adapted to be held on thedrum 10 by a mechanism 26 which is adapted to tension the ink pad.

The tensioning mechanism 26 comprises an elongated hook plate or member28 formed with a plurality of hooks 30 adapted to be received in theopenings 24 provided in the bar 22. The hook plate 23 is arranged toextend longitudinally of the printing drum 10 and is disposed in areceded position with respect to the extended circle of the diaphragm12. The hooks 3i) are aligned with each other along a line extendinglongitudinally of the printing drum 10 and are spaced longitudinallyalong the length of the drum, with a spacing corresponding to that ofthe openings 24.

The hook plate 28 is guided for sliding movement in a generaliyperipheral direction with respect to the printing drum 10. In this case,the hook plate 28 is formed with a pair of elongated slots 32 whichextend in a generally peripheral direction and are parallel to eachother. The plate 28 is supported over and is slidable along a supportingwall 34 which recedes from the periphery of the diaphragm 12. Guide pins36 are mounted on the wall 34 and are arranged to extend outwardlythrough the slots 32. The t between the pins 36 and the slots 32 may befairly loose so that the hook plate 28 will be freely movable.

The hook plate 28 is adapted to be moved by means of an elongatedoperating plate or member 38. As shown, a portion of the operating plate38 overlies a portion of the hook plate 28. The operating plate 38extends lengthwise of the cylinder and is guided for lengthwise slidingmovement. Thus, the illustrated operating plate 38 has a .pair ofelongated slots 40 and 42 which extend lengthwise of the cylinder 10.The guide pins 36 extend outwardly through the longitudinal slots 40.Washers 44 and clips 46 may be mounted on the pins 36 to retain theoperating plate 38 thereon. The t between the pins 36 and the slots 4l)and 42 is sufficiently loose to permit free movement.

In order that the hook plate 28 may be moved peripherally in response tothe longitudinal movement of the operating plate 38, a cam 48 isarranged to act between the plates 28 and 38. In this case, the cam 48takes the form of an elongated diagonal slot in the operating plate 3.8.The slot 48 is adapted to be followed by a roller or pm 50 which ismounted on the hook plate 28 and extends` outwardly into the slot 48.When the operating plate 38 1s moved longitudinally, the diagonal camslot 38 induces peripheral movement of the hook plate 2S.

By means of a spring 52, the operating plate 38 is normally urged in onelongitudinal direction so as to bias the hook plate 28 in a directionsuch as to tension the ink pad 14. Thus, the spring 52 tends to move theoperating plate 38 to the left, as shown in Fig. 3, and thereby tends todraw the hook plate 28 upwardly. In

this case, the spring 52 is of the coil spring type and is tensionedbetween a pin 54 or the like on the operating plate 38 and a pin orother anchor 56 on the cylinder wall 34. lt will be observed that thespring 52 extends longitudinally of the cylinder between the operatingplate 38 and the cylinder wall 34.

At its upper edge, the operating plate 38, as shown in Figs. 3 and 4, isfonned with a generally L-shaped flange 58 which spaces the upperportion of plate 38 from the cylinder wall 34, so as to provide room forthe spring 52. The extreme edge of the flange 58 is retained and guidedunder an enlarged head 60 which is formed on a stud 62 mounted on thecylinder wall 34. in this way, the upper edge of the operating plate 38is kept from swinging away from the cylinder wall 34. The tit betweenthe flange 58 and the stud 62 is quite loose so Vas to provide for freeand easy movement of the operating plate 38. At its right-hand end, theoperating plate 38 is formed with an upstanding lange 64 which serves asa handle or manually moving the operating plate 38.

When the operating plate 38 is moved to the right, as shown in Figs. 3and 5, the hook bar 28 is moved in a direction to relax the tension inthe ink pad 24 and eventually release the ink pad.

1n Fig. 5, the tensioning mechanism 26 is shown in its pad-releasingposition with the operating plate 38 moved fully to lthe right. In orderto detain the mechanism in this position, while the ink pad is beingremoved or replaced, the slot 42 is formed with a detent notch 66 at itsleft-hand end. The notch 66 extends in a peripheral direction anddownwardly as seen in Figs. 3 and 5. When the operating plate 38 isfully moved to the right, as seen in Fig. 5, the right-hand end of theplate may be swung upwardly to engage the notch 66 with the righthandguide pin 36. The engagement between the notch 66 and the guide pin 36will retain the operating plate 38 in the pad-releasing position untilthe operator swings the right-hand end of the operating platedownwardly. It will be understood that the it between the headed stud 62and the upper edge of the operating plate 38 is sufciently loose topermit the slight upward swinging movement which is involved in engagingthe notch 66 with the pin 36. in the course of such swinging movement,the operating plate 38 pivots about the left-hand guide pin 36.

Fig. 2 illustrates the pad-tensioning mechanism 36 in its rest positionoccupied when there is no ink pad on the printing drum 10. In thisposition, the operating plate 38 is moved fully to the left by thespring 52, and the hook plate 28 is moved fully in an upward direction.

When the ink pad is to be installed on the drum 10, the head end of theink pad is hooked over the studs 16 and the pad is wrapped around thediaphragm 12. The operating plate 38 is then fully moved to the right,to move the hook plate 28 fully in a downward direction, as shown inFig. 5. The operating plate is swung upwardly so as to engage the notch66 with the right-hand pin 36. This detains the operating plate in itspadreleasing position. The apertured bar 22 at the head end of the inkpad 14 may then be mounted on the hooks 30.

Tension is applied to the pad 14 by swinging the operating plate 38downwardly to release the notch 66 from the pin 36. The operating plate38 is then allowed to return to the left under the force of the spring52. The hook plate 28 is drawn upwardly until the ink pad 14 is drawntight around the diaphragm 12. The spring 52 maintains tension on theink pad 14 at all times. Fig.

3 shows the tensioning mechanism 26 in its normal operating positionwith the pad 14 held under tension.

It will be seen that the diagonal cam slot 48 supplies the tensioningforce to the hook plate 28 through the medium of the roller 50. The hookplate 28 is free to pivot sufhciently about the roller 50 to equalizethe tension on the various hooks 34). Thus, the engagement between theguide slots 32 and the pins 36 prevents any substantial movement of thehook plate 28 in a lengthwise'direction with respect to the cylinder 10but the t between the slots and the pins is suiciently loose to permitthe hook plate 28 to rock or pivot about the axis of the roller 50. Suchfreedom for pivoting movement assures that the tension in the ink pad 14will be evenly distributed along the width of the pad.

It will be recognized that the tensioning mechanism is extremely easy tooperate yet is highly eiTective in tensioning the pad. Moreover, thetensioning mechanism is easy to manufacture and low in cost.

Various modifications, alternative constructions and equivalents may beemployed without departing from the true spirit and scope of theinvention as exemplified in the foregoing description and defined in thefollowing claim.

I claim:

In a stencil type duplicator, the combination comprising a printingcylinder for receiving an ink pad and a stencil, means for anchoring oneend ot the ink pad to the cylinder, a hook plate for securing theopposite end of the ink pad to the cylinder, said hook plate having aplurality of hooks thereon spaced along the length of the cylinder forconnection of the ink pad to said plate, said hook plate being disposedon said cylinder along the length thereof, a plurality of parallel slotsin said plate, said slots being elongated and arranged to extend in agenerally peripheral direction with respect to said cylinder, aplurality of guide pins secured to said cylinder and extending outwardlythrough said slots to guide said plate for generally peripheral movementon said cylinder, an elongated operating plate extending longitudinallyof said cylinder over said hook plate, said operating plate having aplurality of elongated slots therein extending lengthwise of saidcylinder and received over said guide pins to guide said operating platefor movement longitudinally of said cylinder, said operating platehaving an elongated generally diagonal cam slot therein, a followerroller mounted on said hook plate and extending into f said cam slot formoving said hook plate peripherally in response to longitudinal movementof said operating plate, a spring urging said operating plate in onelongitudinal direction to bias said hook plate in a peripheral directionsuch as to tension the ink pad, said operating plate being movable inthe opposite direction against the-force of the spring to release theink pad, and a notch formed adjacent to one end of one of said guideslots in said operating plate for receiving the corresponding guide pinto detain said operating plate in its pad-releasing position.

References Cited in the tile of this patent UNITED STATES PATENTS1,662,284 Shea Mar. 13, 1928 2,579,517 Rowell et al Dec. 25, 19512,645,177 Dressel et al July 14, 1953 FOREIGN PATENTS 817,308 GermanyOct. 18, 1951

